E 43 Electronic structure and electron-phonon interactions in layered LixNbO2 and NaxNbO2 [Text] / D. L. Novikov, V. A. Gubanov, V. G. Zubkov, A. J. Freeman // Physical Review B: Condensed Matter. - 1994. - V. 49, N 22. - P15830-15835 . - ISSN 0163-1829 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ХИМИЯ -- LixNbO2 -- NaxNbO2 -- ОКСОНИОБАТ ЛИТИЯ -- ОКСОНИОБАТ НАТРИЯ -- СТРУКТУРА ЭЛЕКТРОННАЯ -- ЭЛЕКТРОННАЯ СТРУКТУРА -- ЭЛЕКТРОННО-ФОНОННОЕ ВЗАИМОДЕЙСТВИЕ -- ВЗАИМОДЕЙСТВИЕ ЭЛЕКТРОННО-ФОНОННОЕ Аннотация: Structural, luminescence, and electronic properties of the family of alkaline metal-strontium cyclotetravanadates M2Sr(VO3)4, M=Na, K, Rb, and Cs have been characterized by means of elemental analyses, x-ray powder diffraction, neutron diffraction, electron diffraction, infrared, Raman, photo, x rays, pulse cathode beam excitation, x-ray photoelectron spectroscopy and band structure calculations. The M2Sr (VO3)4 system have tetragonal structures Na-, K-, Rb-P4/nbm and Cs-P4/mmm, with a=10.63449(4), 10.94106(6), 11.08889(8), 7.9183(3) and c=4.96205(4), 5.31600(4), 5.46682(8), 5.5778(3) Å, respectively. The main structural feature of M2Sr(VO3)4 is tetracyclic [V4O12] units. When going from Na2Sr(VO3)4 to Cs2Sr(VO3)4 do the coordination polyhedron around the alkaline metal change continuously from an octahedron to a hexagonal prism and that around the strontium from a square antiprism to a square prism. The hybridized O 2p-V 3d states of tetracyclic [V4O12] units have a dominant influence on the electronic structure of these compounds. All M2Sr(VO3)4 are semiconducting with a decreasing LDA band gap (Ea) from 2.02 for Na2Sr(VO3)4 to 1.56 eV for Cs2Sr(VO3)4 Полный текст |